(Not Applicable.)
The present invention relates to processes and apparatus for measuring fluid flow, and more particularly, to a hot wire anemometer.
An anemometer is an instrument which measures the velocity of the flow of fluids, such as air or other gases, and in some cases of liquids. While mechanical anemometers, such as cup anemometers are useful for measuring wind speed, hot-wire anemometers are required for more technical applications.
Hot-wire anemometers function as thermal transducers which are capable of sensing point flow velocity by means of temperature variations using a heated resistive wire with a nonzero temperature coefficient of resistance. When the electrically heated wire is placed in a flow of fluid, heat is taken away by flow-induced forced convection, i.e., the wire is cooled by the fluid flow. Depending upon the operational mode used, e.g. constant current or constant temperature, either the resistance or the voltage output drop across the wire is then a function of the flow velocity. Thus, in the case of a constant current device, greater flow results in a greater temperature drop over time.
Hot wire anemometers are commonly used to measure air velocity in the vicinity of ventilation ducts in occupied buildings. Ventilation ducts are often mounted near the room ceiling or in an otherwise elevated location. Therefore, for applications such as these, the hot wire anemometer must be extended to reach these areas in order to obtain an accurate measurement. There are a number of products on the market that attempt to accomplish this task by using either telescopic heads or extension handles. However, these devices are not ideal.
One of the most difficult problems in manufacturing a telescopic probe is that the electronics required to interface with the sensors require several electrical conductors, which are most commonly electrically conductive wires, to pass inside the telescopic section. As the head is rotated, the wires twist, and thus, 360xc2x0 rotation is not possible. Also, when the telescopic section is collapsed, the wires also have to retract without snagging. Some manufacturers have attempted to overcome this problem by making telescoping anemometers which have a cable that is not fixed at the probe handle end, with the objective of making the cable free to travel up and down the inside of the telescopic section. These devices require a special cable to be used. The cable is typically stiff and not easy to manage, which also, among other things, limits its length and requires an additional electronics module to interface to the measuring instrument.
The present invention provides a solution to the problems and inconveniences associated with prior art anemometers.
The present invention is directed to an anemometer comprising a support member with an extendable probe portion having two ends and one or more conductors in the extendable probe portion for electrical flow and transfer of data between a data gathering system located at one end of the extendable probe portion and a data processing and command system located in the support member connected to the other end of the extendable probe portion, or in a remote source such as a personal computer.
The preferred embodiment of the inventive anemometer includes a handle and probe. The probe comprises a coaxial telescoping extension having two concentric telescoping sections which are electrically-insulated from each other. Data is gathered by sensors at the probe head end and transferred to a data processor in the handle through the telescoping sections, which comprise the necessary conductors for data and power transfer between the probe head and handle. The probe may be fully rotated and extended to obtain data without being physically obstructed.